Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzyme Btrk Decarboxylase
This subfamily is composed of Bacillus circulans BtrK decarboxylase and similar proteins. These proteins are fold type III PLP-dependent enzymes that contain an N-terminal PLP-binding TIM-barrel domain and a C-terminal beta-sandwich domain, similar to bacterial alanine racemases, eukaryotic ornithine decarboxylases and diaminopimelate decarboxylases. BtrK is presumed to function as a PLP-dependent decarboxylase involved in the biosynthesis of the aminoglycoside antibiotic butirosin. Homodimer formation and the presence of the PLP cofactor may be required for catalytic activity.